Real-time interactive routing using topology-driven line probing

ABSTRACT

Techniques and systems for determining a route from a start point to a target point in an integrated circuit (IC) design using topology-driven line probing are described. Some embodiments can create a data structure to store a set of nodes, wherein each node is located on a horizontal probe or a vertical probe, and wherein each node has a cost. The embodiments can then perform a set of operations in an iterative loop, the set of operations comprising: selecting a lowest cost node from the set of nodes; terminating the iterative loop if the lowest cost node is located at the target point; extending a probe from the lowest cost node if the lowest cost node is not located at the target point; creating at least one new node on the probe or on an ancestor of the probe; and adding the new node to the set of nodes.

RELATED APPLICATION

This application claims benefit of Indian Provisional Application SerialNo. 201811048230, filed on 19 Dec. 2018, the contents of which areherein incorporated by reference in their entirety for all purposes.

COPYRIGHT NOTICE

The assignee of this patent document does not object to the facsimilereproduction of the patent document as it appears in the files of theUnited States Patent and Trademark Office, but otherwise reserves allrights whatsoever in any included works of authorship protected bycopyright.

BACKGROUND Technical Field

This disclosure relates to integrated circuit (IC) design. Morespecifically, this disclosure relates to real-time interactive routingusing topology-driven line probing.

Related Art

Advances in process technology have fueled a rapid increase in the sizeand complexity of IC designs. This dramatic increase in complexity andintegration densities has made it considerably more challenging todesign ICs. IC design tools allow a user to draw routes between circuitobjects to electrically connect the circuit objects. The dramaticincrease in complexity and integration densities has created a need formore powerful and user friendly IC design tools.

SUMMARY

This section is not intended to limit the scope of the disclosed subjectmatter. The disclosed subject matter is to be accorded the widest scopeconsistent with the principles and features disclosed in the entiredisclosure. Some embodiments described herein provide systems andtechniques that feature real-time interactive routing usingtopology-driven line probing.

Specifically, some embodiments can determine a route from a start pointto a target point in an IC design using topology-driven line probing.The embodiments can create a data structure to store a set of nodes,wherein each node is located on a horizontal probe or a vertical probe,and wherein each node has a cost. Next, the embodiments can perform aset of operations in an iterative loop, wherein the set of operationscan comprise: selecting a lowest cost node from the set of nodes,wherein the lowest cost node is located on a first probe; terminatingthe iterative loop if the lowest cost node is located at the targetpoint; extending a second probe from the lowest cost node, wherein thesecond probe is orthogonal to the first probe; storing a parent-childrelationship between the first probe and the second probe; creating atleast one new node on the second probe or an ancestor probe of thesecond probe; and adding the new node to the set of nodes. In someembodiments, the route from the start point to the target point can bedetermined by tracing back a sequence of probes from the target point tothe start point based on the stored parent-child relationships.

In some embodiments, the cost of each node is equal to a sum of (1) afirst cost of a first route from the start point to the node, and (2) alower bound of a second cost of a second route from the node to thetarget point.

In some embodiments, creating at least one new node can comprise: (1)creating at least one new node comprises creating the new node on thesecond probe at a location where the second probe hits an obstacle, (2)creating the new node on the second probe at a location having an Xcoordinate or a Y coordinate of the target point, (3) creating the newnode on an ancestor probe of the second probe (e.g., the first probe, ora parent of the first probe, or a grandparent of the first probe, and soforth) at a location having an X coordinate or a Y coordinate of an edgeof an obstacle encountered by the second probe, and/or (4) creating thenew node on the second probe at a location having an X coordinate or a Ycoordinate of an edge of an obstacle encountered by an ancestor probe ofthe second probe.

In some embodiments, the second probe and the first probe can be ondifferent routing layers of the IC design. In some embodiments, thedifferent routing layers of the IC design have different unit routingcosts.

In some embodiments, the data structure is a priority queue, whereinlower cost corresponds to higher priority so that the lowest cost nodeis a highest priority node in the priority queue.

Some embodiments can receive a sequence of user inputs that define aroute topology in an IC design, wherein the route topology comprises asequence of topology edges and at least one bend or via. The embodimentscan then check if the sequence of topology edges violates one or moredesign rules. If no design rules have been violated, the embodiments candisplay routing shapes corresponding to the route topology. On the otherhand, if one or more design rules have been violated, the embodimentscan move at least one bend or via in the route topology by a minimumdistance required to satisfy the one or more design rules, therebyobtaining a design-rule-violation-free route topology. Next, theembodiments can optionally highlight one or more shapes in the IC designthat caused the sequence of topology edges to violate the one or moredesign rules. The embodiments can then display routing shapescorresponding to the design-rule-violation-free route topology.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates planar routing for a single point-to-point connectionin accordance with some embodiments described herein.

FIGS. 2A-2C illustrate an example of using the Optimal Line Probing(OLP) technique in accordance with some embodiments described herein.

FIG. 3 illustrates propagation in the presence of multiple layers inaccordance with some embodiments described herein.

FIG. 4 illustrates a top view of multiple vertical probes on differentlayers propagating their obstacle coordinates back to a horizontal probein accordance with some embodiments described herein.

FIG. 5 illustrates how different layer costs can be handled inaccordance with some embodiments described herein.

FIG. 6 illustrates how coordinate propagation can be performed inaccordance with some embodiments described herein.

FIG. 7 illustrates an interactive router in accordance with someembodiments described herein.

FIG. 8 illustrates how child probes can be created in accordance withsome embodiments described herein.

FIGS. 9A-9F illustrate the topology as defined by user inputs and whatthe user perceives in accordance with some embodiments described herein.

FIGS. 10A-10B illustrate processes for facilitating real-timeinteractive routing using topology-driven line probing in accordancewith some embodiments described herein.

FIG. 11 illustrates a computer system in accordance with someembodiments described herein.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the claimed invention(s), and is provided in thecontext of particular application(s) and/or environment(s). Variousmodifications to the disclosed embodiments will be readily apparent tothose skilled in the art, and the general principles defined herein maybe applied to other embodiments and applications without departing fromthe spirit and scope of the disclosure. Thus, the disclosed subjectmatter is not limited to the embodiments shown, but is to be accordedthe widest scope consistent with the principles and features disclosedherein.

In this disclosure, numerous specific details may be described to enableone or more of the embodiments. In the interest of not obscuring thepresentation of the embodiments, some features that are known in the artmay be combined together, may be described in less detail, or may beimplied (i.e., some well-known features may not be explicitlydescribed). Furthermore, while this description may refer to somefeatures in the singular tense, more than one instance of the featuremay be illustrated in the figures, and like components are labeled withlike numerals.

An IC design and manufacturing process produces IC chips. IC designsoftware tools can be used to create an IC design. Once the IC design isfinalized, it can undergo fabrication, packaging, and assembly toproduce IC chips. The overall IC design and manufacturing process caninvolve multiple entities, e.g., one company may create the software fordesigning ICs, another company may use the software to create the ICdesign, and yet another company may manufacture IC chips based on the ICdesign. An IC design flow can include multiple steps, and each step caninvolve using one or more IC design software tools. An improvement toone or more of these steps in the IC design flow results in animprovement to the overall IC design and manufacturing process.Specifically, the improved IC design and manufacturing process canproduce IC chips with a shorter time-to-market (TTM) and/or higherquality of results.

As an IC design progresses through an IC design flow, the IC design canbe represented at different levels of abstraction by using differentdata formats or languages. In general, higher levels of abstractioncontain fewer details of the IC design than lower levels of abstraction.Typically, the IC design is described at a high level of abstraction inthe early stages of the IC design flow, and the level of abstractionbecomes progressively lower as the IC design moves through the IC designflow (i.e., the description of the IC design becomes more specific asthe IC design progresses through the IC design flow).

For example, toward the beginning of the IC design flow, an IC designcan be described at a high level of abstraction by using a hardwaredescription language (HDL) which describes the functionality of the ICdesign but does not include information about the actual geometricshapes that will be printed on the wafer. Toward the end of the ICdesign flow, the same IC design can be represented in a low level ofabstraction by using a data format or language such as GDSII or OASIS,which contains a description of the actual geometric shapes that are tobe printed on the wafer. In between these two ends of the IC designflow, the IC design may be represented in numerous data formats orlanguages that describe the same IC design at different levels ofabstraction.

Some examples of IC design steps and the associated software tools aredescribed below. These examples are for illustrative purposes only andare not intended to limit the embodiments to the forms disclosed. Thisdisclosure describes techniques and systems that can be used in one ormore IC design steps.

IC design software tools enable IC designers to describe thefunctionality that the IC designers want to implement. These tools alsoenable IC designers to perform what-if planning to refine functionality,check costs, etc. During logic design and functional verification, theHDL, e.g., SystemVerilog, code can be written and the design can bechecked for functional accuracy, e.g., the design can be checked toensure that it produces the correct outputs.

During synthesis and design for test, the HDL code can be translated toa netlist using one or more IC design software tools. Further, thenetlist can be optimized for the target technology, and tests can bedesigned and implemented to check the finished chips. During netlistverification, the netlist can be checked for compliance with timingconstraints and for correspondence (i.e., equivalence checking) with theRTL design and/or HDL code.

During design planning, an overall floorplan for the chip can beconstructed and analyzed for timing and top-level routing. Duringphysical implementation, circuit elements can be positioned in thelayout and can be electrically connected.

During analysis and extraction, the IC design's functionality can beverified at a transistor level and parasitics can be extracted. Duringphysical verification, the design can be checked to ensure correctnessfor manufacturing, electrical issues, lithographic issues, andcircuitry.

During resolution enhancement, geometric manipulations can be performedon the layout to improve manufacturability of the design. During maskdata preparation, the design can be “taped out” to produce masks whichare used during fabrication.

With increasing system-on-chip integration, automatic routing ofcritical signals at the top level of a chip is becoming an importantfeature in physical design tools. There are two traditional approachesfor performing automated routing: (1) graph-based routing, and (2)shape-based routing. In graph-based routing, all objects in the routingregion are pre-processed and a routing graph is created. A graph searchtechnique is then used to find the shortest path between two points ornodes in the graph. In shape-based routing, probes are extended from thestart point. When a probe hits an obstacle shape, it stops, and newprobes are extended in the perpendicular direction, until the targetpoint is reached.

Graph-based search techniques can guarantee finding the optimal(shortest) route between a pair of points. However, for large designs,the graph creation step can be very expensive in memory and runtime. Ifthis overhead cannot be amortized over a large number of nets, it leadsto an inefficient routing system. Shape-based routers do not have anyup-front graph creation overhead. However, existing shape-basedapproaches do not guarantee that probe expansion will find an optimalpath. This can lead to routes that are sub-optimal or have too manybends, which may be unacceptable for critical top-level routes such asclocks or major buses.

Custom routing is quickly becoming the most time-consuming andeffort-intensive step in the IC design flow. Automating this step isdifficult because the designer must precisely control route shapes toachieve desired electrical characteristics of the circuit. At the sametime, increasingly complex design rules make drawing detailed routesusing a polygon editor extremely tedious. Current custom layoutautomation approaches typically suffer from one of two drawbacks—theyeither do not capture user intent with sufficient detail, or they burdenthe user with having to specify too much detail. In the first case, theautomation results are often undesired or unpredictable, leading torework and lost productivity. In the second case, the automation doesnot add enough value as the user ends up having to do most of the work,again leading to lower productivity.

Given a routing region with multiple layers, a set of rectilinearobstacles, a set of source and target points, embodiments describedherein find a shortest path between each pair of source S and target T,such that the path does not pass through any obstacle. Some embodimentsdescribed herein include the following features and advantages: (1) thestartup time to begin the search is essentially zero, because thetechnique does not require any pre-processing of the region to create agraph, (2) preferred and non-preferred routing orientations aresupported on each layer, and different costs on different layers arealso supported, (3) no assumptions are made about the presence of arouting grid, i.e., if a grid is present, it will be used, but it is notrequired. Finally, and maybe most importantly, the embodiments describedherein can guarantee that the path from S to T is a minimal-cost path.This is a very important feature when routing critical signals andbuses: even a small deviation from the optimal path could impact chiptiming, or waste precious routing area in the floorplan.

Specifically, it can be proven, by using mathematical induction, thatthe routing solution found by the embodiments disclosed herein is indeedoptimal in realistic routing scenarios. Note that the optimality of thesolution does not come at the expense of the runtime—in fact, theembodiments are faster than existing shape-based approaches.

Some embodiments described herein feature an interactive router thatallows the user to define a flexible topology guide on the layoutcanvas. As the user builds up this guide using a sequence of mousemovements and keystrokes, a topology-constrained search engine computesand displays a design rule clean route that deviates minimally from theuser-defined topology. The topology guide itself is invisible to theuser, thereby giving the user the impression of a “What you See Is WhatYou Get” (WYSIWYG) router that follows the cursor in real time with apredictable design-rule-clean route path.

Since the sequence of routing layers used by the router is constrainedto match those in the topology defined by the user, the user has preciseand direct control over the routing result. However, since the routerhas the freedom to deviate from the exact locations of the topologyedges, it can find a design-rule clean path that is as close to thetopology as possible. The user is therefore relieved from the burden ofhaving to understand complex design rules and having to precisely clickon the canvas to satisfy these rules.

The use of the topology-constrained line probe search engine is animportant enabler for the interactive router. The efficiency of lineprobing is further improved in the interactive router by constrainingthe line probe engine to exactly match the sequence of bends and viasspecified in the topology and modifying the objective function tominimize deviation from the specified bend and via locations. Thesechanges further reduce the search space of an already highly efficientrouting process, resulting in a very responsive interface for the useras they move the mouse. Topology-constrained line probing also allowsthe router to scale up very well to large design sizes.

The combination of flexible topology and line probe search has anadditional benefit, which is particularly valued by users. The routesgenerated by the interactive router tend to “hug” the boundaries ofobstacles (such as blockages or previously drawn routes) precisely,resulting in compact layout with no wasted space. This is achievedautomatically, with no special effort required from the user.

For the user, the direct benefits of the embodiments disclosed hereininclude better productivity, compact layout, and reduced strain on theeyes and hands, since the embodiments do not require users to make anyprecise measurements while drawing. From a product developmentperspective, the topology-based approach described herein provides afoundation for implementing multiple advanced editing features,including bus, shield and tandem routing, real-time shove-aside editing,and automatic update of routing when the floorplan changes.

FIG. 1 illustrates planar routing for a single point-to-point connectionin accordance with some embodiments described herein. Consider twopoints S and T in a 2-D plane. Obstacles (which may overlap each other),e.g., obstacles 100, are distributed at various locations in the plane.The objective in the planar routing problem is to find a shortest pathjoining S and T (if a path exists), such that the path does not crossany obstacle.

As mentioned above, routing approaches for solving the planar routingproblem can be broadly classified as graph-based or shape-based.Graph-based approaches pre-process the region to build a routing graph,and then use variations of breadth-first search on the graph to find ashortest path from S to T. Graph-based approaches work well when thereare a large number of nets to be routed, since the runtime and memoryoverhead of the initial graph construction can be amortized over a largenumber of nets. Graph-based algorithms also guarantee that the pathfound will have the minimum cost, which is an important considerationwhen the quality of the route is important.

When a relatively small set of nets needs to be routed, thecomputational overhead of graph-based approaches can be prohibitivelyhigh. In such cases, shape-based approaches are popular, because theseapproaches do not require building a graph up-front. Shape-basedapproaches, such as line probing, typically involve extending probestowards the target, and changing the direction of a probe when the probehits an obstacle. Line probing is a fast technique but does notguarantee that a path will be found even if it exists. Even if a path isfound, there is no guarantee that the path will be optimal. Sub-optimalroutes can cause significant problems for chip timing and area.

Some embodiments describe herein feature an enhanced line probingtechnique that is guaranteed to find a shortest path, if a path exists.The line probing technique that is used in some of the embodiments isreferred to as the OLP technique in this disclosure, and is bothshape-based and optimal, making it ideal for routing critical nets whichrequire high-quality routes. OLP is also very efficient computationallyas it runs several times faster than existing state-of-the-artcommercial shape-based routers.

The OLP technique is first described in the context of a single-layersearch, and then a general multi-layer OLP technique is described thatcan accommodate different horizontal (hereinafter “H”) and vertical(hereinafter “V”) costs on each routing layer.

FIGS. 2A-2C illustrate an example of using the OLP technique inaccordance with some embodiments described herein. The technique canbegin by extending horizontal line probe 202 and vertical line probe 204from the source node S. The origin of these probes is the point S, andthe probes extend from the origin point, all the way to the left/loweredge and the right/upper edge of the routing region.

If a probe hits an obstacle, an end node is created on the probe at thepoint where the line crosses the obstacle boundary. For example, endnode 208 is created when the vertical probe 204 hits obstacle 206. Theprobe segment of the line probe is defined as the part of the probelying between the lower/left and upper/right end nodes (if the probedoes not hit an obstacle in a direction, the probe segment is defined toextend till the region boundary in that direction).

In addition to the end nodes, for any H or V probe, if the probe segmentcontains the target point's X or Y coordinate, a node is created on theprobe at the corresponding X or Y coordinate. In FIG. 2A, the horizontalprobe 202 contains the X coordinate of the target point T, so node 210is created at that point. The vertical probe segment does not cross theY coordinate of T, so no node is created on the vertical probe.

Each node has a cost, which has at least two components: g and h. Thefirst component, g, is the total accumulated cost of reaching node, N,from S, and the second component, h, is the lower bound of estimatedcost of reaching T from N. The value of “g” can be determined bycomputing the cost of each segment along the route from source S to thecurrent location. The value of “h” can be determined by computing theminimum cost of a one or two segment Manhattan route from the currentlocation to T (the minimum cost Manhattan route will have only onesegment if either the X or Y coordinate of the current location matchesthe X or Y coordinate of T; otherwise the minimum cost Manhattan routewill have two segments). If different layers have different costs, thenfor computing the lower bound, the cheapest horizontal cost can beselected for the horizontal segment and the cheapest vertical cost canbe selected for the vertical segment.

FIG. 2B illustrates how new line probes can be expanded. Nodes can beinserted into a priority queue, sorted by their total cost (g+h) (tiesare broken by the lower h cost). In other words, lower cost cancorrespond to higher priority in the priority queue. The lowest costnode N is popped from the queue, and a new line probe Q is expanded,orthogonal to the direction of the owner probe P of N. The probe Q isdefined to be the child of P, and P is the parent of Q.

The expansion depth of a probe P is the number of probes (including P)along the back-trace from P to the first probe in the expansion.

Suppose a vertical probe Q hits obstacle 212 as shown in FIG. 2B. If theX coordinate of the left or right edge of obstacle 212 lies inside theprobe segment of Q's parent P (which is a horizontal probe), then anadditional node is created at that coordinate on P. For example, node214 can be created in this manner in FIG. 2B. Creating nodes in a parent(or ancestor) probe based on the edges of an obstacle that the currentprobe hit is known as backward propagation.

In some cases, such as that shown in FIG. 2C, probe Q may need to knowthe Y-coordinates of the obstacle hit by its parent P. So, each probestores the coordinates of the obstacles that it hits, for forwardpropagation to its children when needed. In forward propagation, a nodeis created in a child (or descendant) probe based on the edges of anobstacle that the current probe hit. For example, in FIG. 2C, probe Phits obstacle 216, and nodes 218 and 220 are created in the child probeQ based on the top and bottom edges of obstacle 216. Note that the edgesof an obstacle are parallel to the probe that was blocked by theobstacle. So, the top and bottom edges of obstacle 216 are used forhorizontal probe P, whereas the left and right edges are used forvertical probe Q.

Nodes are stored in a spatial data structure and marked with a flag whenthey are expanded. Once a node is marked, it cannot be inserted into thepriority queue again. Nodes created by forward and backward propagationare also inserted into the priority queue. The search terminates whenthe node popped from the queue has the same coordinates as the targetpoint. The path from S to T is reconstructed by tracing the probesbackwards from T to S.

A generalization of the planer OLP technique to multiple layers is nowdescribed, wherein successive layer orientations alternate between H andV, and all layer costs are identical. On an H layer, only H probes areexpanded, and vice versa. Transitions from one layer to the next orprevious layer in the stack are made using via probes, whose orientationis either Up or Down (U or D).

As with planar OLP, we start at the source point S, create a node atthat (x, y, z) location, and insert the node into the priority queue. Ateach step, the OLP process pops the lowest cost node N from the queue,and expands a line probe in the orientation of the layer of N, and oneor two via probes. If the predecessor node of N is on the same layer asN (or if N is the source node), then two via probes are expanded—one upand one down. If the predecessor node is on the layer below N, then onlyan up via probe is expanded, else only a down via probe is expanded.

Expanding a line probe P is exactly the same as in the planar case: whenP hits an obstacle, an end node is created at the intersection point. Anode that is aligned with the target is created on the probe if theprobe segment contains the target's X or Y coordinates. The end-nodesand target-aligned nodes are defined to be owned by the line probe P andare inserted into the priority queue.

Expanding a via probe (x, y, z, U/D) from a node N (x, y, z) meanschecking the legality of placing a via-up/via-down at that location. Ifthe via is legal, a node NN is created at (x, y, z±1), and inserted intothe node priority queue. Note that NN inherits its owner probe from N,i.e., only line probes are allowed to own nodes. In the case of astacked via, where vias are placed one on top of the other at the same(x, y) location, we need to trace back through the whole stack to findthe parent line probe. Note that via probes do not participate inparent-child relationships. The parent P of a probe Q originating from anode N is simply the owner probe of the node N: we may need to traceback through via probes until we find a line probe. With this definitionof parent-child relationships between line probes in place, the backwardpropagation procedure can now be defined.

FIG. 3 illustrates propagation in the presence of multiple layers inaccordance with some embodiments described herein. Suppose a verticalprobe Q hits obstacle 302. The X coordinates of obstacle 302 arepropagated to horizontal ancestor probes of Q, by tracing backwardsalong the parent probes until a horizontal ancestor is found whose probesegment does not contain the centerline X coordinate of Q. FIG. 3 showsbackward propagation from a vertical probe Q to a horizontal ancestor P.Arrow 304 indicates a path comprising of multiple via and line probes.Every horizontal segment along this path must contain the X coordinateof Q. As shown in FIG. 3, nodes 308 and 310 were created on ancestorprobe P based on the edges of obstacle 302 that probe Q hit. Nodes 306and 312 were created on ancestor probe P based on the edges of obstacle314 that probe Q hit.

FIG. 4 illustrates a top view of multiple vertical probes on differentlayers propagating their obstacle coordinates back to a horizontal probein accordance with some embodiments described herein. The horizontalprobe P is on one of the layers in the IC design, and the verticalprobes (Q is one of the vertical probes shown in FIG. 4) are on otherlayers. The probe Q does not propagate its coordinates to probe Pbecause probe P does not contain the X coordinate of probe Q.Additionally, probe Q hits obstacle 402, and the edges of obstacle 402are also not back propagated to probe P, as shown in FIG. 4. On theother hand, probe P contains the X coordinates of probe A. Therefore,node 406 is created on probe P that corresponds to the X coordinate ofprobe A. Also, probe A hits obstacle 404, and back propagation is usedto create nodes 408 and 410 on probe P corresponding to the left andright edges of obstacle 404, respectively.

FIG. 5 illustrates how different layer costs can be handled inaccordance with some embodiments described herein. Specifically, someembodiments can handle different layer costs by modifying the coordinatepropagation process. The intuition behind the modification can beunderstood based on the following example. Consider two horizontalprobes P (on layer L) and Q (on layer L+2), as shown in FIG. 5. Let usassume that the cost of layer L is greater than the cost of layer L+2.The route from S to T that is determined by the propagation techniquedescribed above is shown by the solid lines corresponding to probes P,A, and Q. Note that this is not the lowest cost solution. Specifically,sliding the vertical probe to the left (i.e., probe A′ shown with adashed line) would result in a lower cost solution because that solutionhas a shorter length on layer L, which is cheaper than layer L+2. Oneway to modify the propagation technique so that it arrives at thissolution is to propagate the X coordinates of obstacle 502 back to probeP. In other words, in the modified propagation procedure, the Xcoordinates of obstacles hit by horizontal probes are propagated back tohorizontal ancestor probes in addition to being propagated back to thevertical probe ancestors as was the case in the propagation procedurethat was described earlier. Likewise, obstacles hit by vertical probesare propagated back to vertical ancestor probes in addition to beingpropagated back to the horizontal probe ancestors. The modifiedcoordinate propagation procedures thus requires probe obstaclecoordinates to be propagated to both vertical and horizontal ancestorand descendant probes.

FIG. 6 illustrates how coordinate propagation can be performed inaccordance with some embodiments described herein. A procedure forpropagation of X coordinates is described below. A similar processapplies for Y coordinates. If a vertical probe Q_(V) hits an obstacle602, the X coordinates of obstacle 602 are propagated to horizontalancestor probes of Q_(V), by tracing backwards along the parent probesuntil a horizontal ancestor is found whose probe segment does notcontain the centerline X coordinate of Q_(V).

If a horizontal probe Q_(H) hits obstacle 604, the X coordinates ofobstacle 604 are propagated to horizontal ancestor probes of Q_(H), bytracing backwards along the parent probes until a horizontal ancestor isfound whose probe segment does not contain the X coordinate of Q_(H).

The routing process can also be extended to allow bidirectional routing.Since the typical process nodes and routing layers will have a strongpreferred orientation (H or V), with non-preferred direction routinghaving a much higher cost and allowed over shorter distances, thissituation can be handled as follows. Non-preferred direction expansionwill happen through segment probes—short probes whose length isdetermined by factors like track pitch, minimum segment length designrules or width/spacing. As an example, the maximum probe length in thenon-preferred orientation could be limited to two track pitches, with ahigher cost than the preferred orientation. This would be sufficient toescape from off-grid pins or create planar jogs, but not long enough tosignificantly impact optimality of the final solution.

FIG. 7 illustrates an interactive router in accordance with someembodiments described herein. In the context of the interactive router,the term “topology” or “topology object” refers to the route that theuser is trying to create in the IC design tool, and the term “topologyedge” corresponds a single straight line segment of the route.

When the user invokes the Interactive Router (IR) command from the“Router” menu in the graphical user interface (GUI) of the IC designtool, they can start drawing a route in one of two ways. (1) Click on anexisting shape of a net (the term “click” refers to a selectionoperation that can be performed by selecting a button of a pointingdevice (e.g., by pressing the button) that allows a user to move apointer or cursor in the GUI). In this case, the current net, width, andlayer are inherited from the shape, and the start point is computed toalign the route to the shape. (2) Select a net from the “DesignNavigator” section of the GUI (which is a GUI section that allows theuser to browse, search, and select objects in the IC design), a validrouting layer from the “Layer Panel” section of the GUI, and a widthfrom the “Options Toolbar” section of the GUI. Then select any locationon the IC design canvas section of the GUI to indicate the start point.

In the IC design tool, the start point, layer, and current width arerecorded in a topology object. At this stage, the topology comprises asingle point (the start point), and an implicit topology edge joiningthe start point to the current cursor location.

After the start point has been defined by the first click (state 702),the router enters the IR event loop 704 that comprises states 706, 708,and 710. The user can perform the following actions while in the eventloop.

In state 706, canvas events are captured. Specifically, in this state,the user can select keys (e.g., by pressing keys of a pressure-basedkeyboard) to insert bends and vias. For example, a “Shift-v” keystrokecan insert an up-via at the current cursor location, and the topologyobject can be augmented with a new point. Each point has an attributeindicating whether it is a bend, up-via or down-via. Each new point issnapped such that it is either horizontally or vertically aligned to itspredecessor, i.e., every topology edge joining two successive topologypoints is either H or V. The last point in the topology is joined to thecursor location by an implicit topology edge.

In state 706, the user can also move the mouse. As the cursor moves, thetopology is updated in real time to track the cursor location bystretching (or shrinking) the last (implicit) topology edge, and themost recent topology edge perpendicular to the implicit topology edge.Among the possible topology update strategies, this strategy leads tothe most intuitive behavior of the router. In this state, the user canalso change the current width of the route.

Specifically, by using the mouse scroll wheel, the user can increase ordecrease the width of the current route segment to any value that islegal for the current layer. This width is stored as an attribute on themost recent point in the topology object. The “<Backspace>” can be usedto delete the last inserted point from the topology object. If thetopology object only had one point (the start point), then selectingthis key causes the IR to exit the event loop. The user can also selectthe “<Return>” key to save the route created so far to the designdatabase and exit the event loop. Finally, the “<Escape>” key can beselected to discards the current route and exits the IR command.

After an event is captured by the canvas events state 706, the updatedtopology is passed to a topology-constrained line probe (TCLP) router,which attempts to find a design-rule clean route that begins from thestart point and has the exact sequence of bends and vias specified inthe topology. The TCLP algorithm is an extension of the line probeprocess described earlier.

In TCLP, every line probe corresponds to a specific topology edge in thetopology object. The procedure to compute child probes of a line probeis modified as follows. Consider a line probe P corresponding totopology edge k of the topology object. The child probes of P created byTCLP will be on the layer of topology edge (k+1).

FIG. 8 illustrates how child probes can be created in accordance withsome embodiments described herein. In FIG. 8, line probe P and obstacle802 are on the same layer as topology edge k, and child probes P₀, P₁,and P₂, and obstacle 804 are on the same layer as topology edge (k+1).The topology edges are shown using dashed lines, and line probes usingsolid arrows. Probe P is at depth k, i.e., it corresponds to the kthtopology edge. The first child probe P₀ of P will be created on thelayer of topology edge (k+1) at a point on probe P which is as close aspossible to the centerline of topology edge (k+1) (note that a topologyedge can have a width; therefore, the centerline of the topology edge isused for calculating distances so that the distance calculation does notdepend on the width of the topology edge). If this child probe isexpanded and hits obstacle 804, as shown in FIG. 8, this can result inup to two additional child probes P₁ and P₂ that are created on probe P,depending on the dimensions of the obstacle.

The cost of the child probes depends on how much they deviate from thecenterline of their corresponding topology edge. For example, the childprobe P₁ can have a cost equal to the cost of P, plus a costcorresponding to the distance d₁. Child probes are inserted into a probepriority queue sorted by cost. At each step, the lowest cost probe ischosen for expansion. Since, in the example shown in FIG. 8, P₁ has alower cost than P₂, probe P₁ is expanded before probe P₂. The TCLPsearch terminates when the lowest cost probe in the priority queue has adepth equal to N+1, where N is the number of topology edges. This probe,and its chain of predecessor probes of decreasing depth, are returned tothe event loop state machine.

FIGS. 9A-9F illustrate the topology as defined by user inputs and whatthe user perceives in accordance with some embodiments described herein.The route update and display process is now described in reference toFIGS. 9A-9F. After each canvas event, when TCLP computes and returns anew route to the event loop, the previous route is erased from thecanvas and the new route is displayed. The topology creation and updateprocess is invisible to the user—all the user perceives is route shapesfollowing the cursor in real time, in a smooth and predictable way, withvias and bends staying as close as possible to their desired location.For example, FIG. 9A shows the inputs provided by the user through theGUI, and FIG. 9B shows the route shapes that are created and displayedto the user in real time.

When there are obstacles blocking the path, the route gracefully adaptsand finds a solution that “hugs” the obstacle and gets as close to thecursor as possible. This “contouring” behavior is especially beneficialto users as the routes will tend to stay at minimum design rule spacingto obstacles and previously routed nets, without requiring any specialeffort on the part of the user. This results in very compact layout withno wastage of space. In FIG. 9C, as the user moves the mouse up and tothe right, the last two topology edges of the topology stretch, so thatthe topology end point tracks the cursor location. The router is unableto reach the exact cursor location because that point is blocked byshape 902. Instead, as shown in FIG. 9D, TCLP finds a route that stays alegal distance d away from the shape, gets as close to the cursor aspossible, and deviates minimally from the topology bend point by movingthe bend point from location 904 to location 906. The shape preventingthe route from reaching the cursor is highlighted (e.g., by using shadedregion 908 that extends around shape 902), as a visual cue that theroute is “hugging” shape 902 to try and get close to the cursor. Thisillustrates the contouring behavior of the router.

In FIG. 9E, the user continues to move the mouse upwards past shape 902and then to the right. At location 910 of the cursor, the route wouldviolate against obstacles 912 and 902 if it followed the topologyexactly. However, the solution found by TCLP, shown in FIG. 9F, movesboth the via and the bend slightly from their user-specified locations,to find a legal route. Both blocking shapes are highlighted, and theroute hugs both shapes at minimum design rule spacing.

The optimal line probing (OLP) technique, combines the best propertiesof shape-based routers (zero start-up cost) and graph-based routers(guaranteed optimal paths). This technique is ideally suited forfull-chip custom routing: finding high quality routes for a relativelysmall number of critical nets, at the top level of a largesystem-on-chip design. The approach to interactive routing splits up theproblem into two sub-parts—topology creation/update based on userinputs, and topology-constrained line probe search. This strategy leadsto fast, predictable and area-efficient routing, while reducing eye andhand strain for the user. The productivity boost from embodimentsdescribed herein are expected to have a measurable impact on chip designcycle times. Apart from providing direct benefits to users, thetopology-centric approach used in the embodiments described herein alsolays an architectural foundation for interactive routing that enablesone to build powerful new WYSIWYG editing features, such as bus routingwith interleaving, shielded and matched routing, interactive shove-asiderouting, and automatic re-routing when the floorplan changes.

FIGS. 10A-10B illustrate processes for real-time interactive routingusing topology-driven line probing in accordance with some embodimentsdescribed herein.

The process in FIG. 10A can begin by creating a data structure to storea set of nodes, wherein each node is located on a horizontal probe or avertical probe, and wherein each node has a cost (step 1002). In someembodiments, the cost of each node is equal to a sum of (1) a first costof a first route from the start point to the node, and (2) a lower boundof a second cost of a second route from the node to the target point. Insome embodiments, the data structure is a priority queue, wherein lowercost corresponds to higher priority so that the lowest cost node is ahighest priority node.

Next, the process can perform a set of operations in an iterative loop(steps 1004-1014). Specifically, the process can select a lowest costnode from the set of nodes, wherein the lowest cost node is located on afirst probe (step 1004). Next, the process can check if the lowest costnode is located at the target point (step 1006). If so, the process canterminate the iterative loop. Otherwise, the process can extend a secondprobe from the lowest cost node, wherein the second probe is orthogonalto the first probe (step 1008). The process can then store aparent-child relationship between the first probe and the second probe(step 1010).

Next, the process can create at least one new node on the second probeor an ancestor probe of the second probe (step 1012). The process canthen add the new node to the set of nodes (step 1014). Next, the processcan return back to step 1004 to perform the next iteration of theiterative loop. Specifically, in step 1012, the process can create theat least one new node by: (1) creating at least one new node comprisescreating the new node on the second probe at a location where the secondprobe hits an obstacle, (2) creating the new node on the second probe ata location having an X coordinate or a Y coordinate of the target point,(3) creating the new node on an ancestor probe of the second probe(e.g., the first probe, or a parent of the first probe, or a grandparentof the first probe, and so forth) at a location having an X coordinateor a Y coordinate of an edge of an obstacle encountered by the secondprobe, and/or (4) creating the new node on the second probe at alocation having an X coordinate or a Y coordinate of an edge of anobstacle encountered by an ancestor probe of the second probe.

Note that the second probe and the first probe can be on differentrouting layers of the IC design, and the different routing layers of theIC design can have different unit routing costs.

After the iterative loop terminates, the process can determine the routefrom the start point to the target point by tracing back a sequence ofprobes from the target point to the start point based on the storedparent-child relationships.

The process in FIG. 10B can begin by receiving a sequence of user inputsthat define a route topology in an IC design, wherein the route topologycomprises a sequence of topology edges and at least one bend or via(step 1052). Next, the process can check if the sequence of topologyedges violates one or more design rules (step 1054). If no design ruleshave been violated, the process can display routing shapes correspondingto the route topology (step 1056). On the other hand, if one or moredesign rules have been violated, the process can move at least one bendor via in the route topology by a minimum distance required to satisfythe one or more design rules, thereby obtaining adesign-rule-violation-free route topology (step 1058). Next, the processcan highlight one or more shapes in the IC design that caused thesequence of topology edges to violate the one or more design rules (step1060). The process can then display routing shapes corresponding to thedesign-rule-violation-free route topology (step 1062).

FIG. 11 illustrates a computer system in accordance with someembodiments described herein. The term “computer” or “computer system”generally refers to a hardware-based system that can performcomputations required for the design and manufacture of ICs. Computersystem 1102 can include processor 1104, memory 1106, and storage device1108. Computer system 1102 may include multiple processors, andprocessor 1104 may include multiple cores. Specifically, memorylocations in memory 1106 can be addressable by processor 1104, therebyenabling processor 1104 to access (e.g., via load/store instructions)and manipulate (e.g., via logical/floating point/arithmeticinstructions) the data stored in memory 1106. Computer system 1102 canbe coupled to display device 1114, keyboard 1110, and pointing device1112. Storage device 1108 can store operating system 1116, softwareapplication 1118, and data 1120. Data 1120 can include input required bysoftware application 1118 and/or output generated by softwareapplication 1118.

Computer system 1102 may automatically (or with user help) perform oneor more operations that are implicitly or explicitly described in thisdisclosure. Specifically, computer system 1102 can load softwareapplication 1118 into memory 1106, and software application 1118 canthen be used to create routes in an IC design. The resulting IC designis expected to have better performance and/or quality of results (QoR)because the routes were created by an IC routing tool that featuresreal-time interactive routing using topology-driven optimal lineprobing.

While ‘data’ and ‘information’ often are used interchangeably (e.g.,‘data processing’ and ‘information processing’), the term ‘datum’(plural ‘data’) typically signifies a representation of the value of ameasurement of a physical quantity (e.g., the current in a wire), or theanswer to a question (e.g., “yes” or “no”), while the term ‘information’typically signifies a structured set of data (often times signified by‘data structure’). A specified data structure is used to structure anelectronic device to be used as a specific machine as an article ofmanufacture (see In re Lowry, 32 F.3d 1579 [CAFC, 1994]). Data andinformation are physical, for example binary data (a ‘bit’, usuallysignified with ‘0’ and ‘1’) enabled with two different levels of voltagein a circuit. For example, data can be enabled as an electrical,magnetic, optical or acoustical signal; a quantum state such as spinthat enables a ‘qubit’; or a physical state of an atom or molecule. Allsuch data and information, when enabled, are stored, accessed,transferred, combined, compared, or otherwise acted upon, actions thatrequire energy.

As used herein, the term ‘process’ signifies an unnatural sequence ofphysical actions and/or transformations (both also referred to as‘operations’ or ‘steps’) to produce at least one result. The actions andtransformations are technical applications of one or more natural lawsof science or unnatural laws of technology. The actions andtransformations often change the physical state of a machine, ofstructures of data and information, or of a composition of matter. Twoor more actions can occur at about the same time, or one action canoccur before or after another action, if they produce the same result. Adescription of the physical actions and/or transformations that comprisea process are often signified with a set of gerund phrases (or theirsemantic equivalents) that are typically preceded with the signifier‘the steps of (e.g., “a process comprising the steps of measuring,transforming, partitioning and then distributing . . . ”). Thesignifiers ‘algorithm’, ‘method’, ‘procedure’, ‘(sub)routine’,‘protocol’, ‘recipe’, and ‘technique’ often are used interchangeablywith ‘process’, and 35 U.S.C. 100 defines a “method” as one type ofprocess that is, by statutory law, always patentable under 35 U.S.C.101. Many forms of knowledge, learning, skills and styles are authored,structured, and enabled—objectively—as processes—e.g., knowledge andlearning as functions in knowledge programming languages. As usedherein, the term ‘rule’ signifies a process with at least oneconditional test (signified, e.g., by ‘IF test THEN process’). As usedherein, the term ‘thread’ signifies a sequence of operations orinstructions that comprise a subset of an entire process. A process canbe partitioned into multiple threads that can be used at or about at thesame time.

As used herein, the term ‘component’ (also signified by ‘part’, andtypically signified by ‘element’ when described in a patent text ordiagram) signifies a physical object that is used to enable a process incombination with other components. For example, electronic componentsare used in processes that affect the physical state of one or more(‘ensemble’) electromagnetic or quantum particles/waves (e.g.,electrons, photons) or quasiparticles (e.g., electron holes, phonons,magnetic domains) and their associated fields or signals. Electroniccomponents have at least two connection points to which are attached‘leads’, typically a wire with one end attached to the component and theother end attached to another component, typically as part of a circuitwith current flows. There are at least three types of electricalcomponents: passive, active and electromechanical. Passive electroniccomponents typically do not introduce energy into a circuit—suchcomponents include resistors, memristors, capacitors, magneticinductors, crystals, Josephson junctions, transducers, sensors,antennas, waveguides, etc. Active electronic components require a sourceof energy and can inject energy into a circuit—such components includesemiconductors (e.g., diodes, transistors, optoelectronic devices),vacuum tubes, batteries, power supplies, displays (e.g., LEDs, LCDs,lamps, CRTs, plasma displays). Electromechanical components affectcurrent flow using mechanical forces and structures—such componentsinclude switches, relays, protection devices (e.g., fuses, circuitbreakers), heat sinks, fans, cables, wires, terminals, connectors andprinted circuit boards. As used herein, the term ‘netlist’ is aspecification of the components comprising an electric circuit, andelectrical connections between the components. The programming languagefor the SPICE circuit simulation program is often used to specify anetlist. In the context of circuit design, the term ‘instance’ signifieseach time a component is specified in a netlist.

One of the most important components as goods in commerce is theintegrated circuit, and its res of abstractions. As used herein, theterm ‘integrated circuit’ signifies a set of connected electroniccomponents on a small substrate (thus the use of the signifier ‘chip’)of semiconductor material, such as silicon or gallium arsenide, withcomponents fabricated on one or more layers. Other signifiers for‘integrated circuit’ include ‘monolithic integrated circuit’, ‘IC’,‘chip’, ‘microchip’ and ‘System on Chip’ (‘SoC’). Types of integratedcircuits include gate/logic arrays, processors, memories, interfacechips, power controllers, and operational amplifiers. The term ‘cell’ asused in electronic circuit design signifies a specification of one ormore components, for example, a set of transistors that are connected tofunction as a logic gate. Cells are usually stored in a database, to beaccessed by circuit designers and design processes.

As used herein, the term ‘module’ signifies a tangible structure foracting on data and information that typically is limited in size and/orcomplexity.

For example, the term ‘module’ can signify one or more processes thattransforms data and information, for example, processes comprising acomputer program. The term ‘module’ also can signify one or moreinterconnected electronic components, such as digital logic devices. Aprocess comprising a module, if specified in a programming language,such as System C or Verilog, also can be transformed into aspecification for a structure of electronic components that transformdata and information that produce the same result as the process. Thislast sentence follows from a modified Church-Turing thesis, which issimply expressed as “Whatever can be transformed by a (patentable)process and a processor, can be transformed by a (patentable) equivalentset of modules.”, as opposed to the doublethink of deleting only one ofthe “(patentable)”.

A module is permanently structured (e.g., circuits with unalterableconnections), temporarily structured (e.g., circuits or processes thatare alterable with sets of data), or a combination of the two forms ofstructuring. Permanently structured modules can be manufactured, forexample, using Application Specific Integrated Circuits (‘ASICs’) suchas Arithmetic Logic Units (‘ALUs’), Programmable Logic Arrays (‘PLAs’),or Read Only Memories (‘ROMs’), all of which are typically structuredduring manufacturing. For example, a permanently structured module cancomprise an integrated circuit. Temporarily structured modules can bemanufactured, for example, using Field Programmable Gate Arrays(FPGAs—for example, sold by Xilink or Intel's Altera), Random AccessMemories (RAMs) or microprocessors. For example, data and information istransformed using data as an address in RAM or ROM memory that storesoutput data and information. One can embed temporarily structuredmodules in permanently structured modules (for example, a FPGA embeddedinto an ASIC).

Modules that are temporarily structured can be structured duringmultiple time periods. For example, a processor comprising one or moremodules has its modules first structured by a manufacturer at a factoryand then further structured by a user when used in commerce. Theprocessor can comprise a set of one or more modules during a first timeperiod, and then comprise a different set of one or modules during asecond time period. The decision to manufacture or implement a module ina permanently structured form, in a temporarily structured form, or in acombination of the two forms, depends on issues of commerce such ascost, time considerations, resource constraints, tariffs, maintenanceneeds, national intellectual property laws, and/or specific designgoals. How a module is used is mostly independent of the physical formin which it is manufactured or enabled. This last sentence also followsfrom the modified Church-Turing thesis.

As used herein, the term ‘processor’ signifies a tangible data andinformation processing machine for use in commerce that physicallytransforms, transfers, and/or transmits data and information, using atleast one process. A processor comprises one or more modules (e.g., acentral processing unit, ‘CPU’; an input/output (‘I/O’) controller, amemory controller, a network controller, and other modules). The term‘processor’ can signify one or more processors, or one or moreprocessors with multiple computational cores/CPUs, specializedprocessors (for example, graphics processors or signal processors), andtheir combinations. Where two or more processors interact, one or moreof the processors can be remotely located. Where the term ‘processor’ isused in another context, such as a ‘chemical processor’, it will besignified and defined in that context.

The processor can comprise, for example, digital logic circuitry (forexample, a binary logic gate), and/or analog circuitry (for example, anoperational amplifier). The processor also can use optical signalprocessing, DNA transformations or quantum operations, microfluidiclogic processing, or a combination of technologies, such as anoptoelectronic processor. For data and information structured withbinary data, any processor that can transform data and information usingthe AND, OR and NOT logical operations (and their derivatives, such asthe NAND, NOR, and XOR operations) also can transform data andinformation using any function of Boolean logic. A processor such as ananalog processor, such as an artificial neural network, also cantransform data and information. No scientific evidence exists that anyof these technological processors are processing, storing and retrievingdata and information, using any process or structure equivalent to thebioelectric structures and processes of the human brain.

The one or more processors also can use a process in a ‘cloud computing’environment, where time and resources of multiple remote computers areshared by multiple users or processors communicating with the computers.For example, a group of processors can use at least one processavailable at a distributed or remote system, these processors using acommunications network (e.g., the Internet, or an Ethernet) and usingone or more specified interfaces (e.g., an application program interface(‘API’) that signifies functions and data structures to communicate withthe remote process).

As used herein, the term ‘computer’ and ‘computer system’ (furtherdefined below) includes at least one processor that, for example,performs operations on data and information such as (but not limited to)the AND, OR and NOT logical operations using electronic gates that cancomprise transistors, with the addition of memory (for example, memorystructured with flip-flops using the NOT-AND or NOT-OR operation). Sucha processor is Turing-complete and computationally universal. A computercan comprise a simple structure, for example, comprising an I/O module,a CPU, and a memory that performs, for example, the process of inputtinga signal, transforming the signal, and outputting the signal with nohuman intervention.

As used herein, the term ‘programming language’ signifies a structuredgrammar for specifying sets of operations and data for use by modules,processors and computers. Programming languages include assemblerinstructions, instruction-set-architecture instructions, machineinstructions, machine dependent instructions, microcode, firmwareinstructions, state-setting data, or either source code or object codewritten in any combination of one or more higher level languages, forexample, the C programming language and similar general programminglanguages (such as Fortran, Basic, Javascript, PHP, Python, C++),knowledge programming languages (such as Lisp, Smalltalk, Prolog, orCycL), electronic structure programming languages (such as VHDL,Verilog, SPICE or SystemC), text programming languages (such as SGML,HTML, or XML), or audiovisual programming languages (such as SVG,MathML, X3D/VRML, or MIDI), and any future equivalent programminglanguages. As used herein, the term ‘source code’ signifies a set ofinstructions and data specified in text form using a programminglanguage. A large amount of source code for use in enabling any of theclaimed inventions is available on the Internet, such as from a sourcecode library such as Github.

As used herein, the term ‘program’ (also referred to as an ‘applicationprogram’) signifies one or more processes and data structures thatstructure a module, processor or computer to be used as a “specificmachine” (see In re Alappat, 33 F3d 1526 [CAFC, 1991]). One use of aprogram is to structure one or more computers, for example, standalone,client or server computers, or one or more modules, or systems of one ormore such computers or modules. As used herein, the term ‘computerapplication’ signifies a program that enables a specific use, forexample, to enable text processing operations, or to encrypt a set ofdata. As used herein, the term ‘firmware’ signifies a type of programthat typically structures a processor or a computer, where the firmwareis smaller in size than a typical application program, and is typicallynot very accessible to or modifiable by the user of a computer. Computerprograms and firmware are often specified using source code written in aprogramming language, such as C. Modules, circuits, processors,programs, and computers can be specified at multiple levels ofabstraction, for example, using the SystemC programming language, andhave value as products in commerce as taxable goods under the UniformCommercial Code (see U.C.C. Article 2, Part 1).

A program is transferred into one or more memories of the computer orcomputer system from a data and information device or storage system. Acomputer system typically has a device for reading storage media that isused to transfer the program, and/or has an interface device thatreceives the program over a network. This process is discussed in theGeneral Computer Explanation section.

The signifier ‘commercial solution’ signifies, solely for the followingparagraph, an engineering domain-specific (and thus non-preemptive—seeBilski): electronic structure, a process for a specified machine, amanufacturable circuit (and their Church-Turing equivalents) or acomposition of matter that applies science and/or technology in commerceto solve a technical problem.

The signifier ‘abstract’ (when used in a patent claim for any enabledembodiments disclosed herein for a new commercial solution that is ascientific use of one or more laws of nature {see Benson}, and thatsolves a problem of technology {see Diehr} used in commerce—or improvesupon an existing commercial solution {see Diehr})—is precisely definedby the inventor(s) {see MPEP 2111.01 (9th edition, Rev. 08.2017)} asfollows:

a) a new commercial solution is ‘abstract’ if it is not novel (e.g., itis so well known in equal prior art {see Alice} and/or the use ofequivalent prior art solutions is long prevalent {see Bilski} inscience, engineering or commerce), and thus unpatentable under 35 U.S.C.102, for example, because it is ‘difficult to understand’ {seeMerriam-Webster definition for ‘abstract’} how the commercial solutiondiffers from equivalent prior art solutions; or

b) a new commercial solution is ‘abstract’ if it is obvious, that is, ifthe existing prior art includes at least one analogous prior artsolution {see KSR}, or the existing prior art includes at least twoprior art publications that can be combined {see Alice} by a skilledperson {often referred to as a ‘PHOSITA’, see MPEP 2141-2144 (9thedition, Rev. 08.2017)} to be equivalent to the new commercial solution,and is thus unpatentable under 35 U.S.C. 103, for example, because it is‘difficult to understand’ how the new commercial solution differs from aPHOSITA-combination/-application of the existing prior art; or

c) a new commercial solution is ‘abstract’ if it is not disclosed with adescription that enables its praxis, either because insufficientguidance exists in the description, or because only a genericimplementation is described {see Mayo} with unspecified components,parameters or functionality, so that a PHOSITA is unable to instantiatean embodiment of the new solution for use in commerce, without, forexample, requiring special programming {see Katz} (or, e.g., circuitdesign) to be performed by the PHOSITA, and is thus unpatentable under35 U.S.C. 112, for example, because it is ‘difficult to understand’ howto use in commerce any embodiment of the new commercial solution.

The Detailed Description signifies in isolation the individual features,structures, functions, or characteristics described herein and anycombination of two or more such features, structures, functions orcharacteristics, to the extent that such features, structures, functionsor characteristics or combinations thereof are enabled by the DetailedDescription as a whole in light of the knowledge and understanding of askilled person, irrespective of whether such features, structures,functions or characteristics, or combinations thereof, solve anyproblems disclosed herein, and without limitation to the scope of theClaims of the patent. When an embodiment of a claimed inventioncomprises a particular feature, structure, function or characteristic,it is within the knowledge and understanding of a skilled person to usesuch feature, structure, function, or characteristic in connection withother embodiments whether or not explicitly described, for example, as asubstitute for another feature, structure, function or characteristic.

In view of the Detailed Description, a skilled person will understandthat many variations of the claimed inventions can be enabled, such asfunction and structure of elements, described herein while remaining inthe domain of the claimed inventions. One or more elements of anembodiment can be substituted for one or more elements in anotherembodiment, as will be understood by a skilled person. Writings aboutembodiments signify their uses in commerce, thereby enabling otherskilled people to similarly use in commerce.

This Detailed Description is fitly written to provide knowledge andunderstanding. It is neither exhaustive nor limiting of the precisestructures described, but is to be accorded the widest scope consistentwith the disclosed principles and features. A skilled person can enablemany equivalent variations. Without limitation, any and all equivalentsdescribed, signified or Incorporated By Reference in this patentapplication are specifically Incorporated By Reference into the DetailedDescription. In addition, any and all variations described, signified orIncorporated By Reference with respect to any one claimed invention andits embodiment also are included with all other claimed inventions andtheir embodiments. Any such variations include both currently knownvariations as well as future variations, for example any element usedfor enablement includes a future equivalent element that provides thesame function, regardless of the structure of the future equivalentelement.

It is intended that the domain of the set of claimed inventions andtheir embodiments be defined and judged by the following Claims andtheir equivalents. The Detailed Description includes the followingClaims, with each Claim standing on its own as a separate claimedinvention. The embodiments of the claimed inventions can have morestructure and features than are explicitly specified in the Claims.

The foregoing embodiments have been presented for purposes ofillustration and description. They are not intended to be exhaustive orto limit the scope of this disclosure to the forms disclosed.Accordingly, many modifications and variations will be apparent topractitioners skilled in the art. Additionally, the above disclosure isnot intended to limit the disclosed subject matter. The scope of theclaimed invention(s) is defined by the appended claims.

What is claimed is:
 1. A non-transitory computer-readable storage mediumstoring instructions that, when executed by a computer, cause thecomputer to perform a method for determining a route from a start pointto a target point in an integrated circuit (IC) design usingtopology-driven line probing, the method comprising: creating a datastructure to store a set of nodes, wherein each node is located on ahorizontal probe or a vertical probe, and wherein each node has a cost;and performing a set of operations in an iterative loop, the set ofoperations comprising: selecting a lowest cost node from the set ofnodes, wherein the lowest cost node is located on a first probe;terminating the iterative loop if the lowest cost node is located at thetarget point; extending a second probe from the lowest cost node,wherein the second probe is orthogonal to the first probe; storing aparent-child relationship between the first probe and the second probe;creating at least one new node on the second probe or an ancestor probeof the second probe; and adding the new node to the set of nodes.
 2. Thenon-transitory computer-readable storage medium of claim 1, wherein thecost of each node is equal to a sum of (1) a first cost of a first routefrom the start point to the node, and (2) a lower bound of a second costof a second route from the node to the target point.
 3. Thenon-transitory computer-readable storage medium of claim 1, wherein saidcreating at least one new node comprises creating the new node on thesecond probe at a location where the second probe hits an obstacle. 4.The non-transitory computer-readable storage medium of claim 1, whereinsaid creating at least one new node comprises creating the new node onthe second probe at a location having an X coordinate or a Y coordinateof the target point.
 5. The non-transitory computer-readable storagemedium of claim 1, wherein said creating at least one new node comprisesone or more of: (1) creating the new node on an ancestor probe of thesecond probe at a location having an X coordinate or a Y coordinate ofan edge of an obstacle encountered by the second probe, and (2) creatingthe new node on the second probe at a location having an X coordinate ora Y coordinate of an edge of an obstacle encountered by an ancestorprobe of the second probe.
 6. The non-transitory computer-readablestorage medium of claim 1, wherein the second probe and the first probeare on different routing layers of the IC design.
 7. The non-transitorycomputer-readable storage medium of claim 6, wherein the differentrouting layers of the IC design have different unit routing costs. 8.The non-transitory computer-readable storage medium of claim 1, whereinthe data structure is a priority queue, wherein lower cost correspondsto higher priority so that the lowest cost node is a highest prioritynode in the priority queue.
 9. The non-transitory computer-readablestorage medium of claim 1, wherein the method further comprisesdetermining the route from the start point to the target point bytracing back a sequence of probes from the target point to the startpoint based on the parent-child relationships.
 10. A method fordetermining a route from a start point to a target point in anintegrated circuit (IC) design using topology-driven line probing, themethod comprising: creating, by using a computer, a data structure tostore a set of nodes, wherein each node is located on a horizontal probeor a vertical probe, and wherein each node has a cost; and performing aset of operations in an iterative loop, the set of operationscomprising: selecting a lowest cost node from the set of nodes, whereinthe lowest cost node is located on a first probe; terminating theiterative loop if the lowest cost node is located at the target point;extending a second probe from the lowest cost node, wherein the secondprobe is orthogonal to the first probe; storing a parent-childrelationship between the first probe and the second probe; creating atleast one new node on the second probe or an ancestor probe of thesecond probe; and adding the new node to the set of nodes.
 11. Themethod of claim 10, wherein the cost of each node is equal to a sum of(1) a first cost of a first route from the start point to the node, and(2) a lower bound of a second cost of a second route from the node tothe target point.
 12. The method of claim 10, wherein said creating atleast one new node comprises creating the new node on the second probeat a location where the second probe hits an obstacle.
 13. The method ofclaim 10, wherein said creating at least one new node comprises creatingthe new node on the second probe at a location having an X coordinate ora Y coordinate of the target point.
 14. The method of claim 10, whereinsaid creating at least one new node comprises one or more of: (1)creating the new node on an ancestor probe of the second probe at alocation having an X coordinate or a Y coordinate of an edge of anobstacle encountered by the second probe, and (2) creating the new nodeon the second probe at a location having an X coordinate or a Ycoordinate of an edge of an obstacle encountered by an ancestor probe ofthe second probe.
 15. The method of claim 10, wherein the second probeand the first probe are on different routing layers of the IC design.16. The method of claim 15, wherein the different routing layers of theIC design have different unit routing costs.
 17. The method of claim 10,wherein the data structure is a priority queue, wherein lower costcorresponds to higher priority so that the lowest cost node is a highestpriority node in the priority queue.
 18. The method of claim 10, whereinthe method further comprises determining the route from the start pointto the target point by tracing back a sequence of probes from the targetpoint to the start point based on the parent-child relationships.
 19. Anapparatus, comprising: a processor; and a non-transitorycomputer-readable storage medium storing instructions that, whenexecuted by the processor, cause the apparatus to perform a method fordetermining a route from a start point to a target point in anintegrated circuit (IC) design using topology-driven line probing, themethod comprising: creating a data structure to store a set of nodes,wherein each node is located on a horizontal probe or a vertical probe,and wherein each node has a cost; and performing a set of operations inan iterative loop, the set of operations comprising: selecting a lowestcost node from the set of nodes, wherein the lowest cost node is locatedon a first probe; terminating the iterative loop if the lowest cost nodeis located at the target point; extending a second probe from the lowestcost node, wherein the second probe is orthogonal to the first probe;storing a parent-child relationship between the first probe and thesecond probe; creating at least one new node on the second probe or anancestor probe of the second probe; and adding the new node to the setof nodes.
 20. The apparatus of claim 19, wherein the data structure is apriority queue, wherein lower cost corresponds to higher priority sothat the lowest cost node is a highest priority node in the priorityqueue, wherein the second probe and the first probe are on differentrouting layers of the IC design, wherein the different routing layers ofthe IC design have different unit routing costs, and wherein the cost ofeach node is equal to a sum of (1) a first cost of a first route fromthe start point to the node, and (2) a lower bound of a second cost of asecond route from the node to the target point.